As the trial of a Moroccan man accused of stabbing his daughter to death in an honour killing opened in the northern Italian city of Udine on Monday, a Muslim politician said all Italians "are on the side of women".

El Ketawi Dafani is facing murder charges after allegedly stabbing his 18-year-old daughter to death for falling in love with an Italian man in the small town of Montereale Valcellina, northwest of Trieste.

Sanaa Dafani was stabbed in the throat in September, while she was sitting in a car with her 31-year-old boyfriend.

Souad Sbai, an Italian MP for prime minister Silvio Berlusconi's People of Freedom Party, who heads the Association for Moroccan Women in Italy, attended the opening day of the trial on Monday.

"Our presence here doesn't only honour the memory of Sanaa, whose only guilt was being free, but it is a symbol of our fight to protect women locked up in their homes deprived of their dignity," said Moroccan-born Sbai in a statement.

"Women too often pay with their lives because of their desire to determine their own existence," said Sbai, who attended the trial's opening day with other members of her group.

Italian media reports said that Muslim El Ketawi Dafani, objected to religious differences between his daughter and her boyfriend and their plans to live together.